The useless word, for which men will have to answer on the Day of Judgment, is not, therefore, every and any useless word; it is rather the useless, empty word pronounced by him who should instead pronounce the "energetic" words of God. It is, in sum, the word of the false prophet, who has not received the word of God, but nevertheless persuades others to believe his merely human words are the word of God. What happens is exactly the reverse of what St. Paul says: Having received a human word, it is not taken for what it is, but for what it is not, that is, a divine word. For every useless word about God, man will have to answer! This, then, is the meaning of Jesus’ grave admonishment.
The Rev. Raniero Cantalamessa, 2008 Lenten sermon given in the presence of Pope Benedict XVI.